B787 flight crew reported a GPS jamming and/or spoofing event that resulted in the loss of some communications; GPS malfunction and failure; and inaccurate clock times. Additionally; there were false EPGWS warnings that had to be disabled during final approach.
Synopsis
B787 flight crew reported a GPS jamming and/or spoofing event that resulted in the loss of some communications; GPS malfunction and failure; and inaccurate clock times. Additionally; there were false EPGWS warnings that had to be disabled during final approach.
Narrative
Upon returning to the flight deck after our first break we were in the vicinity of Prague. Person A and Relief Pilot briefed us that the GPS had been jammed and one GPS remained failed while the other was intermittent. The second one failed completely somewhere over the Atlantic. In addition when previous crew tried to log onto CPDLC using Aeronautical Telecommunication Network (ATN); the system would drop them off as soon as they were connected. It became evident as we began to set up to request our oceanic clearance that the aircraft clocks were indicating four minutes and 35 seconds later than the actual time. We confirmed time with ATC.We notified Dispatch of our issue and they sent a copy of a long standing NOTAM instructing us that we could continue as long as we notified EGGX of our situation. In response; EGGX gave us a more southerly entry point and did not allow any altitude changes in the crossing. While we were able to login to EGGX successfully; and EGGX did receive our first position report over the entry point; SOMAX; they called on HF to question us about the times and because of the inaccurate times; we had to make the remaining position reports on HF. Once out over the Atlantic; we found that we no longer had ACARS; SATCOM; or any other way to communicate with the company. Later; we found that we could not communicate with EGGX through CPDLC. HF seemed to be the only mode of communication left for us. The EICAS listed: DATALINK LOST; TERR POS; SATVOICE LOST; NO LAND 3 and GPS. One further note; I happened to look down at the center tuning and control panel which was in NAV mode at the time. It was indicating that we were a full degree east of the position indicated on the Navigation Display (ND). Our EFBs were showing us a mile and a half south of the ND position.While we were able to cross the Atlantic successfully; the real issue came on final approach at about 800 feet when we got the TOO LOW TERRAIN" GPWS warning. At the time; we had a clear view of the runway; the airport environment; the terrain below us; the ILS indications; and; very likely; the controller's radar to know with great certainty that we were where we were supposed to be. Because of that; the deteriorating weather at destination and our alternates and the knowledge that the position information was compromised; we elected to disable the warning and land.Causal factors: Apparently the problem was caused by GPS jamming around Turkey which is the norm. Typically; the GPS recovers; but recently; the jamming has been bad enough that the systems are not recovering.Recommendations: Something needs to be done about GPWS warnings when position isn't valid. This is not the first highly inappropriate terrain warning caused by GPS jamming. Perhaps there are reasons not to; but I think Boeing should consider instructing us to disabling the GPWS when the aircraft's position cannot be determined with some accuracy. We should also remove the statement; "Ground proximity alerts that occur are valid;" from the TERR POS ECL and QRH checklists. If some reset procedure or a way to get the GPSs to reset on their own could be implemented; it would be a great help."
Second reporter narrative
Acting as Relief Captain during flight from ZZZZ to ZZZ. Approaching Turkey we began to experience GPS failures associated with spoofing. Additional failures included sporadic and ultimately failure of CPDLC and datalink communications and ultimately EPGWS no terrain" failure. All the appropriate checklists were run multiple times during my time on the flight deck as PIC as failures disappeared and recurred. Upon returning from my second break over the Atlantic Ocean; all GPS had failed; datalink had failed; and terrain position had failed. ANP began to approach 10.0; for which we had requested and received relief over the North Atlantic random route. Position reports were made via HF. Sporadic restoration of datalink allowed us to contact Dispatch for some advice from Maintenance. No constructive advice was available other than the phenomenon was not resettable. Completely unaltered via the checklist was the fact that the ship's clock was now off by 5 minutes; which could have affected position reporting had we not noticed the discrepancy with our EFBs. ANP improved dramatically as we approached the Maritime provinces and DME position updating resumed. Datalink was again sporadically available but GPS and terrain never recovered. Most troubling were the false EPGWS warnings experienced on approach; completely unexpected and not in any of the relevant checklists we ran. The lack of complete descriptions of the possible result of these failures in the checklists is completely unsatisfactory and a potential safety hazard. Cause: Failure to adequately describe in the checklists the potential issues associated with these system failures. Failure of adequate information regarding possible ramifications of GPS jamming/spoofing on the 787."
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.